Bacteriophages are a promising alternative for curtailing infections caused by multi drug resistant (MDR) bacteria. The objective of the present study is to evaluate phage populations from water bodies to inhibit planktonic and biofilm mode of growth of drug resistant Klebsiella pneumoniae in vitro and curtail planktonic growth in vivo in a zebrafish model. Phage specific to K. pneumoniae (MTCC 432) was isolated from Ganges River (designated as KpG). One-step growth curve, in vitro time kill curve study and in vivo infection model were performed to evaluate the ability of phage to curtail planktonic growth. Crystal violet assay and colony biofilm assay were performed to determine the action of phages on biofilms. KpG phages had a greater burst size, better bactericidal potential and enhanced inhibitory effect against biofilms formed at liquid air and solid air interfaces. In vitro time kill assay showed a 3 log decline and a 6 log decline in K. pneumoniae colony counts, when phages were administered individually and in combination with streptomycin, respectively. In vivo injection of KpG phages revealed that it did not pose any toxicity to zebrafish as evidenced by liver/brain enzyme profiles and by histopathological analysis. The muscle tissue of zebrafish, infected with K. pneumoniae and treated with KpG phages alone and in combination with streptomycin showed a significant 77.7% and 97.2% decline in CFU/ml, respectively, relative to untreated control. Our study reveals that KpG phages has the potential to curtail plantonic and biofilm mode of growth in higher animal models.

BackgroundCD3-targeted T cell engagers are potent anti-tumor therapies, but their development often requires management of cytokine release syndrome (CRS). Subcutaneous dosing is a promising strategy to reduce CRS, but its application is limited by its increased immunogenicity risks. Subcutaneous dosing is hypothesized to mitigate CRS by reducing the maximum drug concentration (Cmax) and preserve efficacy by maintaining the same minimum drug concentration (Cmin) as intravenous dosing. A T cell engager designed to be dosed intravenously but engineered to mimic the PK properties of subcutaneous dosing could alleviate CRS without increasing immunogenicity.MethodsTriTAC-XR molecules are engineered T cell engager prodrugs that become slowly activated in systemic circulation. This extended-release mechanism results in a slow build-up of circulating active drug, similar to subcutaneous dosing, and extends drug exposure to enable longer dosing intervals. The prodrug was engineered by adding a peptide mask and protease-cleavable linker to the N-terminus of a TriTAC, a constitutively active and half-life extended T cell engager. The mask binds to the anti-CD3ε domain and prevents T cell binding. Upon cleavage by systemic proteases, active T cell engager is released. Binding was assessed using ELISA on recombinant CD3ε protein and using flow cytometry on primary T cells. T cell engager function was assessed using T cell-dependent cellular cytotoxicity (TDCC) assays with resting human T cells. Safety and efficacy were modeled in non-human primates.ResultsTriTAC-XR had markedly reduced binding to recombinant CD3ε protein and to primary T cells as well as reduced potency in functional TDCC assays compared to its unmasked active drug. In cynomolgus monkeys, TriTAC-XR had significantly attenuated cytokine production while maintaining comparable pharmacodynamic effects as a non-masked active drug. The ratio of Cmax to Cmin for the active TriTAC-XR was significantly smaller than a non-masked control.ConclusionsTriTAC-XR is activated in a time released manner by systemic proteases to minimize differences between the Cmax and Cmin of systemic active drug. This mechanism is different from other protease-activated T cell engager prodrugs that are only activated by tumor-associated proteases. Compared to canonical T cell engagers, TriTAC-XR is expected to improve safety by reducing CRS and to provide convenience by extending dosing intervals.

Bacteriophages are a promising alternative for curtailing infections caused by multi drug resistant (MDR) bacteria. The objective of the present study is to evaluate phage populations from water bodies to inhibit planktonic and biofilm mode of growth of drug resistant Klebsiella pneumoniae in vitro and curtail planktonic growth in vivo in a zebrafish model. Phage specific to K. pneumoniae (MTCC 432) was isolated from Ganges River (designated as KpG). One-step growth curve, in vitro time kill curve study and in vivo infection model were performed to evaluate the ability of phage to curtail planktonic growth. Crystal violet assay and colony biofilm assay were performed to determine the action of phages on biofilms. KpG phages had a greater burst size, better bactericidal potential and enhanced inhibitory effect against biofilms formed at liquid air and solid air interfaces. In vitro time kill assay showed a 3 log decline and a 6 log decline in K. pneumoniae colony counts, when phages were administered individually and in combination with streptomycin, respectively. In vivo injection of KpG phages revealed that it did not pose any toxicity to zebrafish as evidenced by liver/brain enzyme profiles and by histopathological analysis. The muscle tissue of zebrafish, infected with K. pneumoniae and treated with KpG phages alone and in combination with streptomycin showed a significant 77.7% and 97.2 % decline in CFU/ml, respectively, relative to untreated control. Our study reveals that KpG phages has the potential to curtail plantonic and biofilm mode of growth in vivo in higher animal models.

CD3-targeted T cell engagers are potent anti-tumor therapies, but their development often requires management of cytokine release syndrome (CRS). One strategy to reduce CRS is subcutaneous dosing, which is hypothesized to mitigate CRS by reducing the maximum drug concentration (Cmax) and preserve efficacy by maintaining the same minimum drug concentration (Cmin) as intravenous dosing. Although promising for mitigating CRS, this approach is limited by its increased immunogenicity risks. A T cell engager designed to be dosed intravenously but engineered to mimic the PK properties of subcutaneous dosing could alleviate CRS without increasing immunogenicity. Here we describe TriTAC-XR, a platform of T cell engager prodrugs designed to become slowly activated in systemic circulation. This extended-release mechanism results in a slow build-up of circulating active drug and minimizes the Cmax/Cmin ratio, similar to subcutaneous dosing. TriTAC-XR prodrugs were engineered by adding a peptide mask and protease-cleavable linker to the N-terminus of a TriTAC, a constitutively active and half-life extended T cell engager. The mask binds to the anti-CD3ε domain and inhibits T cell binding. Upon cleavage by systemic proteases, active T cell engager is released. In vitro, TriTAC-XR has markedly reduced binding to recombinant CD3ε protein and to primary T cells as well as reduced potency in functional T cell-dependent cellular cytotoxicity (TDCC) assays compared to its unmasked active drug. In cynomolgus monkeys, TriTAC-XRs targeting multiple tumor antigens resulted in a gradual build-up of active drug during the first week post dose and significantly lower Cmax/Cmin ratios than comparable constitutively active TriTACs. Modeling based on these PK data predicts that TriTAC-XR dosed intravenously will result in a slower build-up of active drug and smaller Cmax/Cmin ratios than TriTAC dosed intravenously or subcutaneously. Cytokine release and target cell depletion in cynomolgus monkeys were used to compare the therapeutic index of TriTAC-XR to TriTAC. A single dose of FLT3-targeting TriTAC-XR resulted in 100-fold protection in cytokine release and similar FLT3 expressing cell depletion when compared to an equivalent FLT3-targeting TriTAC. Similarly, repeat dosing of a TriTAC-XR targeting B cells resulted in complete B cell depletion with substantially lower cytokines than a comparable TriTAC. TriTAC-XR is expected to improve the safety of T cell engagers by reducing CRS and may increase clinical dosing convenience by enabling higher doses that will extend dosing intervals. Citation Format: Kathryn Strobel Kwant, Sony S. Rocha, Timothy Yu, Katrina Stephenson, Raphaela Rose Banzon, Sydney Vollhardt, Golzar Hemmati, Evan Callihan, Wade H. Aaron, Subramanian Thothathri, Jessica O'Rear, Eric Bragg, Willis Kwong, Hubert Situ, Avneel Hundal, Stephen Yu, Taggra Jackson, Kevin Carlin, Yinghua Xiao, Maria Rosalyn Dayao, Linh To, Nick Bergo, Kevin Wright, Richard Austin, Holger Wesche, Bryan Lemon, S. Jack Lin. TriTAC-XR: An extended-release T cell engager platform designed to minimize cytokine release syndrome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2861.

Bacteriophages are a promising alternative for curtailing infections caused by multi drug resistant (MDR) bacteria. The objective of the present study is to evaluate phage populations from water bodies to inhibit planktonic and biofilm mode of growth of drug resistant Klebsiella pneumoniae in vitro and curtail planktonic growth in vivo in a zebrafish model. Phage specific to K. pneumoniae (MTCC 432) was isolated from Ganges river (designated as KpG). One-step growth curve, in vitro time kill curve study and in vivo infection model were performed to evaluate the efficacy of phage against planktonic growth. Crystal violet assay and colony biofilm assay was done to determine the action of phages on biofilms. KpG phages had a greater burst size, better bactericidal potential and enhanced inhibitory effect against biofilms formed at liquid air and solid air interfaces. In vivo injection of KpG phages revealed that it did not pose any toxicity to zebrafish as evidenced by liver/brain enzyme profiles and by histopathological analysis. In vitro time kill assay showed a 3 log decline and a 6 log decline in K. pneumoniae colony counts, when phages were administered individually and in combination with streptomycin, respectively. The muscle tissue of zebrafish, infected with K. pneumoniae and treated with KpG phages showed a significant 2 log decline in bacterial counts relative to untreated control. Our study reveals that KpG phages has the potential to curtail plantonic and biofilm mode of growth in vivo in higher animal models.

Tumor-associated calcium signal transducer 2 (Trop2) is a cell surface glycoprotein that promotes cell renewal, proliferation and tumorigenesis. Trop2 is homogenously overexpressed in numerous solid tumor types, including breast, head and neck, prostate, bladder, and non-small cell carcinoma; however, Trop2 is also expressed in several normal tissues, including skin, respiratory tract, and female reproductive organs. Although Trop2-targeted antibody drug conjugates (ADCs) have demonstrated clinical activity, with regulatory approvals in subsets of breast and bladder cancers, their broader utility is still hampered by off-target payload-mediated toxicities. To address this issue, and to avoid on-target off-tumor toxicities, we developed a Trop2-targeting ProTriTAC™ (Protease-activated Tri-specific T cell Activating Construct), a T cell engager prodrug which is engineered to be preferentially activated in tumor tissue. ProTriTACs consists of three humanized antibody-derived binding domains on a single polypeptide chain: anti-albumin for half-life extension, anti-CD3 for T cell engagement, and anti-target antigen for tumor cell engagement. The anti-albumin domain, bearing a masking moiety and a protease-cleavable linker, keeps the prodrug inert by inhibiting binding of the adjacent anti-CD3 domain to T cells. Cleavage of the linker by tumor-associated proteases removes the anti-albumin domain along with the masking moiety to reveal a potent active drug that directs T cell killing within the tumor. As designed, in vitro binding and functional assays show that the protease-activated T cell engager has >1000-fold improved binding to primary human T cells and ~100-fold improved T cell killing compared to its intact masked prodrug. In immunodeficient mice reconstituted with human T cells, anti-Trop2 ProTriTAC demonstrated robust anti-tumor activity in multiple xenograft tumor models, including HCC70 (breast), CAL27 (head and neck), and HPAFII (pancreatic), with complete tumor regression as low as 30 μg/kg. To determine the potential toxicity and toxicokinetic characteristics of anti-Trop2 ProTriTAC, an intra-animal dose escalation was conducted in cynomolgus monkeys until individual maximum tolerated dose (MTD). The starting dose was 20 μg/kg with weekly 3-fold dose escalations until MTD. The one-month study revealed that anti-Trop2 ProTriTAC was tolerated at the 180 μg/kg dose level, but not at the next higher dose level of 540 μg/kg. Toxicokinetics, gross pathology, histopathology, and cytokine data will be presented. The preclinical activity in rodent tumor models, coupled to its tolerability in cynomolgus monkeys, support the development of anti-Trop2 ProTriTAC as a therapeutic in a broad range of Trop2-expressing solid tumors. Citation Format: Sony S. Rocha, Regina Lin, Maria R. Dayao, Raphaela Rose Banzon, Subramanian Thothathri, Kevin J. Wright, Wade Aaron, Yinghua Xiao, Nick Bergo, Linh To, Mabel Bush, Manasi Barath, Timothy Yu, Willis Kwong, Hubert Situ, Eric Bragg, Jessica O'Rear, Kevin Carlin, Stephen Yu, Maritza Solorio, Bryan Lemon, Richard Austin, Holger Wesche, S. Jack Lin. TROP2 ProTriTAC™, a protease-activated T cell engager prodrug targeting TROP2 for the treatment of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2928.

Integrin-β6 (ITGB6) is a transmembrane protein that partners exclusively with the integrin-αV subunit to form the integrin-αVβ6 heterodimer. Due to its roles in tissue remodeling and cancer pathogenesis, therapeutic targeting of integrin-αVβ6 has been investigated for both fibrotic diseases and cancers. ITGB6 is homogenously overexpressed in numerous solid tumor types, including breast, head and neck, pancreatic, and non-small cell lung cancers. Additionally, its expression is an unfavorable prognostic marker in multiple cancers. However, past attempts to therapeutically target ITGB6 have been hindered by its expression in several normal tissues, including bladder, skin, lung, kidney, and muscle. For example, clinical testing of an integrin αVβ6-targeting monoclonal antibody was discontinued reportedly due to toxicity concerns. To reduce on-target/off-tumor toxicities from ITGB6 expression in normal tissues and to enable safe targeting of ITGB6 in solid tumors, we developed an ITGB6-targeting ProTriTAC™ (Protease-activated Tri-specific T cell Activating Construct), a T cell engager prodrug which is engineered to be preferentially activated in tumor tissue. ProTriTACs consists of three humanized antibody-derived binding domains on a single polypeptide chain: anti-albumin for half-life extension, anti-CD3 for T cell engagement, and anti-target antigen for tumor cell engagement. The anti-albumin domain, bearing a masking moiety and a protease-cleavable linker, keeps the prodrug inert by inhibiting binding of the adjacent anti-CD3 domain to T cells. Cleavage of the linker by tumor-associated proteases removes the anti-albumin domain along with the masking moiety to reveal a potent active drug that directs T cell killing within the tumor. As designed, in vitro binding and functional assays show that the protease-activated T cell engager has >1000-fold improved binding to human T cells and ~100-fold improved T cell killing compared to the intact masked prodrug. In immunodeficient mice reconstituted with human T cells, anti-ITGB6 ProTriTAC demonstrated robust anti-tumor activity in multiple ITGB6-expressing xenograft tumor models, including HCC70 (breast), CAL27 (head and neck), and HPAFII (pancreatic), with complete tumor regression as low as 30 μg/kg. To determine the potential toxicity and toxicokinetic characteristics of anti-ITGB6 ProTriTAC, an intra-animal dose escalation was conducted in cynomolgus monkeys. Starting at 20 μg/kg with weekly 3-fold dose escalations, anti-ITGB6 ProTriTAC was well tolerated up to 540 μg/kg, which was the highest dose tested. The preclinical activity in rodent tumor models, coupled to its tolerability in cynomolgus monkeys, support the development of anti-ITGB6 ProTriTAC as a therapeutic in a broad range of ITGB6-expressing solid tumors. Citation Format: Regina J. Lin, Sony S. Rocha, Maria R. Dayao, Subramanian Thothathri, Raphaela Rose Banzon, Kevin J. Wright, Wade Aaron, Yinghua Xiao, Nick Bergo, Linh To, Mabel Bush, Manasi Barath, Yi Yang, Timothy Yu, Willis Kwong, Hubert Situ, Eric Bragg, Jessica O'Rear, Kevin Carlin, Stephen Yu, Maritza Solorio, Bryan Lemon, Richard Austin, Holger Wesche, S. Jack Lin. ITGB6 ProTriTAC™, a protease-activated T cell engager prodrug targeting Integrin-β6 for the treatment of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2927.

Bacteriophages are a promising alternative for curtailing infections caused by multi drug resistant (MDR) bacteria. The objective of the present study is to evaluate phage populations from water bodies to inhibit planktonic and biofilm mode of growth of drug resistant Klebsiella pneumoniae in vitro and curtail planktonic growth in vivo in a zebrafish model. Phage specific to K. pneumoniae (MTCC 432) was isolated from Ganges river (designated as KpG). One-step growth curve, in vitro time kill curve study and in vivo infection model were performed to evaluate the efficacy of phage to curtail planktonic growth. Crystal violet assay and colony biofilm assay was done to determine the action of phages on biofilms. KpG phages had a greater burst size, better bactericidal potential and enhanced inhibitory effect against biofilms formed at liquid air and solid air interfaces. In vivo injection of KpG phages revealed that it did not pose any toxicity to zebrafish as evidenced by liver/brain enzyme profiles and by histopathological analysis. In vitro time kill assay showed a 3 log decline and a 6 log decline in K. pneumoniae colony counts, when phages were administered individually and in combination with streptomycin, respectively. The muscle tissue of zebrafish, infected with K. pneumoniae and treated with KpG phages showed a significant 2 log decline in bacterial counts relative to untreated control. Our study reveals that KpG phages has the potential to curtail plantonic and biofilm mode of growth in vivo in higher animal models.